Enthalpy Heat Exchanger

ABSTRACT

The invention relates to a counter flow enthalpy exchanger ( 1 ) having a parallelogram-shaped central part ( 11 ), whose ends in the flow direction through the exchanger it is joined by end parts ( 12, 13 ), which become narrower in the direction from the central part ( 11 ), whereby in order to separate the flow of the heat-transfer medium in the direction from the inner space to the outer space are arranged contour identical and with respect to the flowing medium sealed vapour-permeable lamellae ( 10 ) with shaping means for generating turbulent flow, whereby every two adjacent lamellae ( 10 ) form one interplate flow channel in the central part ( 11 ) one interplate flow channel. The lamella ( 10 ) is made as a one-piece self-supporting moulding common to the central part ( 11 ) and the end parts ( 12, 13 ), whereby it does not have a reinforcing support grid. Two adjacent lamellae ( 10 ) form one interplate flow channel in the end part ( 12, 13 ), in the walls of which are formed straight protrusions ( 121, 131 ) situated in the direction of the heat-transfer medium flow between the central part ( 11 ) and corresponding inlet or outlet of this medium.

TECHNICAL FIELD

A counter-flow enthalpy exchanger, having a parallelogram-shaped centralpart, at whose ends it is joined in the flow direction through theexchanger by end parts which become narrower in the direction from thecentral part, whereby for the separation of the flow of the heattransfer medium in the direction from the inner space to the outer spaceare arranged vapour-permeable lamellae with identical contours which aresealed with respect to the flowing medium and have shaping means forgenerating turbulent flow. Moreover, every two adjacent lamellae in thecentral part form one inter-plate flow channel.

BACKGROUND ART

Known are regenerative heat exchangers, through which a heat transfermedium flows countercurrent inside spaces which are separated from eachother by heat transfer walls.

An example of such a regenerative system is a device according todocument WO2013091099A1. Heat-transfer surfaces of the actual exchangerare water vapour-permeable pleated sheets stacked in layers on top ofeach other in such a manner that they form a system of parallel channelswhich are separated from each other. Through them flow against eachother the warmer fluid giving off heat and vapour and the cooler fluidreceiving heat and vapour. The outlets and inlets are performed by meansof distribution systems connected to both sides of the exchanger. Theabove-mentioned device is substantially characterized by laminar flow ofthe heat-transfer medium in the straight channels of the exchanger.However, this is not favorable especially with regard to the efficiencyof the exchanger itself. Moreover, the structure of the individuallayers formed by connecting the actual heat-transfer surface to thesystem of fluid supply and exhaust is relatively complicated.

The exchanger according to patent CZ 300299 B6 comprises a frame inwhich are arranged layers of thin lamellae, in which is alternately ledthe air exiting the room and the air entering the room. Each of thelamellae has an inlet and outlet area for the flowing medium in its endparts. The middle part of the lamellae is formed by channels whose taskis to change the direction and velocity of the air flow, since theturbulence of a gaseous medium significantly increases the efficiency ofheat exchange. The material of the walls of the lamellae is a thin metalor plastic film. Such a material has sufficient rigidity and thereforethere is no need to reinforce it by frames or other reinforcingelements. This is advantageous with respect to achieving the maximumpossible area of the efficient surface of the exchanger.

Nevertheless, apart from heat exchange, and in the winter season apartfrom heating the supply air by the exhaust air, the requirement thatdevices for air-conditioning of enclosed spaces should meet isprevention of moisture leakage. By making use of the exiting heat it isnecessary to prevent moisture loss in this case and pass it from thestream of the exiting air to the supplied air. The devices fulfillingthis task are the so-called enthalpy exchangers. It is evident thatbetween the exiting and entering air there cannot be dividing walls thatare impermeable to the air or moisture.

Between two separated inner spaces of a counter-flow enthalpy exchanger,through which the air flows in counter-current configuration, it isnecessary to use a wall with a function of a membrane permeable to watervapour and not to the air. The air exiting the heated space transfersheat and at the same time also moisture to the air entering the room,which has a positive effect of preventing drying of the air in the room.Due to low rigidity of the material of the vapour-permeable membranes itis required that the membrane is reinforced by a supporting means towhich it is attached.

The supporting part of a lamella of an enthalpy exchanger according tothe background art is formed by reinforcing supporting distance grids,which form rigid plastic skeletons coated with a material fulfilling thefunction of a vapour-permeable membrane. Owing to the fact that themembrane is glued onto the skeleton, the skeleton decreases thefunctional area of the lamella, thereby decreasing the efficiency ofboth heat and moisture transfer.

The aim of the invention is to increase the efficiency of the enthalpyexchanger without increasing outer dimensions of the exchanger andwithout a significant increase in the costs of production of itslamellae.

PRINCIPLE OF THE INVENTION

The aim of the invention is achieved by an enthalpy exchanger comprisingflow lamellae for two counter-flow streams of the medium, whoseprinciple is the fact that a lamella is made as a self-supportingmoulding of the central part and end parts without a reinforcingsupporting grid, whereby the lamella is vapour-permeable. Such lamellaedo not contain reinforcing elements, for example grids which decreasethe heat-transfer and vapour-transfer area.

The end parts of the lamella comprise protrusions situated in thedirection the heat-transfer medium flow between the central part and acorresponding inlet or outlet of this medium. That decreases resistanceto the flow in these sections, by which means the effectiveness of theexchanger is higher.

The self-supporting moulding is composite, whereby one of its componentsis formed by a supporting nonwoven layer, which is connected to avapour-permeable membrane. In a preferred embodiment, the material ofthe vapour-permeable membrane is sulfonated block copolymer, which hasvery good properties in terms of vapour permeability, strength anddimensional stability both in dry and wet conditions.

The connection of the supporting nonwoven layer with thevapour-permeable membrane is accomplished by moulding or welding orgluing or dipping. This is favourable from the point of view oftechnology, since it can be performed on known coating or laminatingdevices.

The lamellae are mutually connected at least in some parts of thecircumference by welding or gluing by means of airtight weld joints. Inthis manner, it is possible to obtain a perfect separation of theincoming and outgoing medium in an economical manner.

Preferably, the lamella is made by pressing from a planar blank heldalong the circumference between forming plates having a temperaturehigher than 40° C.

DESCRIPTION OF DRAWINGS

The device according to the invention is schematically represented inthe drawing, where

FIG. 1 shows an oblique view of an enthalpy exchanger with thedirections of the working medium flow,

FIG. 2 illustrates a lateral view of the enthalpy exchanger from FIG. 1in the direction P1,

FIG. 3 shows a plan view of a lamella,

FIG. 4a shows a cross-section C-C from FIG. 3, FIG. 4b represents adetail of the curve of the protrusions of the central part of thelamella from FIG. 3,

FIG. 5 shows an oblique view of the part of the exchanger comprisingfour lamellae in their joined state and

FIG. 6 is a detail of the end part from FIG. 5.

SPECIFIC DESCRIPTION

An enthalpy exchanger is a device serving to transfer heat and humidityfrom a gaseous medium coming out of the inner working space to a gaseousmedium coming from the outer space into the inner space.

The basic constructional element of an enthalpy exchanger 1 according tothe invention is a profiled plate, hereinafter referred to as a lamella10. The lamellae 10 are stacked in layers on top of each other, wherebyadjacent lamellae are along part of their circumferences connected toeach other. Thus, alternating flow interplate spaces arise between pairsof lamellae 10 forming channels 2 for the flow of a gaseous medium inthe direction A from the enclosed space to the outer space and channels3 for the flow of the gaseous medium in the direction B from the outerspace to the enclosed space. These lamellae allow heat transfer from theheated and humid medium which is taken away, e.g., from anair-conditioned space to a cool and usually dry medium supplied fromoutside. The lamellae 10 is substantially a moulding made of a planarblank comprising protrusions and recesses on both sides.

A set of lamellae 10 is inserted and fixed in a casing 100 of theenthalpy exchanger 1. Both outer lamellae 10′, which are adjacent to theside walls inside the casing 100, contribute to the desired character ofthe medium flow in both end flow spaces, heat and moisture exchangethrough them virtually does not occur.

A diagram of the exchanger is shown in FIGS. 1 and 2. In these hatchedare the areas between the lamellae 10, or 10′, the areas between inletor outlet nozzles in the flow inter-plate spaces, while the closed flowinter-plate spaces are not hatched.

The lamella 10 consists of two components. The first component is asupporting layer of nonwoven fabric, which is coated with avapour-permeable membrane. Preferably, the membrane is made ofsulfonated block polymer. The connection of the supporting nonwovenlayer with the vapour-permeable membrane is accomplished by moulding orgluing or dipping. Sulfonated block polymer is advantageous with respectto the degree of vapour permeability, rigidity and dimensional stabilityboth in dry and wet conditions. Moreover, it is also advantageous interms of the production technology of the membrane, which can beimplemented on known coating or laminating devices. Thus, protrusionsand recesses can be formed by compressing in the area of the resultinglamella, their purpose being to generate turbulent flow of the mediumpassing through the gap which constitutes a flow channel between twoadjacent lamellae 10 10′. Generally, turbulent flow increases heattransfer and moisture passage efficiency of the flowing medium separatedby the lamella.

A major advantage is the self-supporting structure of the lamella 10.This structure does not contain a reinforcing grid, which in otherstructures decreases the efficient area for the exchange of heat andhumidity between the exhaust and supply stream of the gaseous medium.

One clear area in the casing 100 of the exchanger 1 is formed by twolamellae 10, which have the same area contour but which differ by thedirection of the bending of peripheral edges, by means of which thelamellae are mutually connected. In the description of the shape, todistinguish these two types according to requirements, they will behereinafter referred to as lamella 10 x and 10 y.

In an exemplary embodiment, the central part 11 of the lamella 10 hasthe shape substantially of a square or rectangle, which is joined in thedirection of the length of the lamella by the end part 12, 13, whosearea becomes narrower in the direction from the central part. In anillustrative embodiment, the areas of the end parts are triangular. Thisfacilitates an arrangement of the input and output flow of the mediumthrough the exchanger diagonally (see FIG. 1). The flow space betweentwo adjacent lamellae 10 is not divided by any closed partition. It is,of course, possible for the shape of the central part to be also arectangle or rhomboid with, for example, adjoining unequal-sidedtriangles of the end parts 12, 13.

The central part 11 of the lamella 10 x is in an example of embodimentaccording to FIG. 3 shaped by longitudinal parallel undulatedprotrusions 111. The curve of their ridges 111′ is in the plane of thesurface of the lamella 10 substantially a sinusoid Sx. The distancebetween two neighbouring ridges 111′ is a pitch R. The ridges 111′ ofthe protrusions 111 are indicated by the solid line, recesses in themiddle between them form protrusions on the other side of the lamella10. The cross-section C-C of the central part from FIG. 3 is shown inFIG. 4a . In an exemplary embodiment, the height v of the wave of theprotrusions 111, that is the maximum thickness of the lamella 10, is 3.5mm. The sinusoid Sx of the ridge 111′ of the protrusions 111 starts inthe part adjacent to the end part 12 with a lower peak DV. In the partadjacent to the end part 13 the sinusoid Sx ends with an upper peak HV.

In the case of the lamella 10 x of the first type, the edge 123 of theend part 12 (in FIG. 3 up on the left) is bent upwards, the second edge124 of the end part 12 is bent downwards. The edge 133 of the endtriangular part 13 parallel to the edge 123 of the end triangular part12 is bent upwards, while the edge 134 of the end triangular part 13parallel to the edge 124 of the end triangular part 12 is bentdownwards.

In the case of the lamella 10 y of the second type, the sinusoid Sy ofthe ridge 111″ of the protrusions 111 is shifted relative to theposition of the sinusoid Sx of the lamella 10 x by half the length λ ofthe wave of the sinusoid Sx, Sy so that it begins in the part adjacentto the end part 12 with the upper peak HV and in the part adjacent tothe end part 13 ends with the sinusoid Sy with the lower peak DV (FIG.4b ). At the points where the sinusoid Sx and Sy cross or touch eachother, the adjacent ridges 111′, 111″ touch each other as well.

The end triangular parts 12, 13 are provided with moulded straightelongated discontinuous protrusions 121, 131, which have the directionof the medium flow in this part of the flow space and which on theopposite side of the lamella form recesses 122,132, which do not worsenthe flow on this opposite side of the lamella, although they areperpendicular to this direction.

The height of the protrusions 121, 131 and recesses 122, 132 of the endparts 12, 13 is at the most 1.7 mm.

The thickness and planar dimensions of the lamella 10, the height of theprotrusions 121, 131, the height v of the wave of the undulated centralpart 11 in the embodiments according to the technical solution (notshown) may change, without exceeding the scope of protection defined bypatent claims.

In the case of the lamella 10 y of the second type, the edge 123 of theend part 12, which is parallel to the protrusions 121, is bentdownwards, whereas the second edge 124 of the end part 12 is bentupwards. The edge 133 of the end triangular part 13 which is parallel tothe edge 123 of the end triangular part 12, is bent downwards, while theedge 134 of the end triangular part 13, which is parallel to the edge124 of the end triangular part 12, is bent upwards.

FIGS. 5 and 6 illustrate stacking the individual lamellae 10 on top ofeach other and their connection. In an exemplary embodiment, theenthalpy exchanger 1 comprises twenty lamellae 10. FIG. 4 illustratesfour lamellae, which are indicated from top to bottom as 10 x ₁, 10 y ₂,10 x ₃, 10 y ₄. FIG. 6 shows a detail of the left side of the set of thelamellae.

The circumferences of the assembled lamellae touch along thelongitudinal sides 112 of the central part 11, where they are cement,forming opposite walls 113 of the casing 100 of the exchanger 1.Similarly, also the ends of the end parts forming the narrow faces 114of the casing 100.

Adjacent lamellae 10 are alternately closed by the edges 123, 124, 133,134 according to FIGS. 5 and 6. The edges 123, 124, 133, 134 areconnected by welding or gluing.

On the left-hand side of FIG. 5 and FIG. 6 there are welded edges 123 ofthe lamellae 10 y ₂, 10 x ₃, by which means the space between theselamellae is closed, whereas between the edges 123 of the lamellae 10 x ₁and 10 y ₂ the inlet into or outlet out of the space is opened. Alsobetween the edges 124 of the lamellae 10 x ₃ and 10 y ₄ there is aninlet or outlet opening. Further on, there is an illustration of twowelded edges 124 of the lamellae 10 x ₁ and 10 y ₂, 10 x ₃ and 10 y ₄.

On the right-hand side of FIG. 5 there is a visible welded joint of theedges 133 of the lamellae 10 y ₂ and 10 x ₃ and inlet nozzles betweenthe edges 133 of the lamellae 10 x ₁ and 10 y ₂, 10 x ₃ and 10 y ₄. Onthe contrary, the invisible art of the circumference of the end part 13contains analogically to a part of the circumference of the end part 12with the edges 124 (a front view in FIG. 6) two welded edges 134 of thelamellae 10 x ₁ and 10 y _(y), 10 x ₃ and 10 y ₄. Between the edges 134of the lamellae 10 y ₂, 10 x ₃ there is also an inlet or outlet opening.

Beside the major advantage, which is the self-supporting structure ofthe lamella 10 and therefore the absence of a reinforcing grid, theenthalpy exchanger 1 entails an advantage of a relatively long path, onwhich the exchange of heat and humidity between counterflow streams ofthe medium takes place. Beside irregularities of the surface of thelamellae 10 of the central part 11 contributing to a considerable extentto the effectiveness of the exchange of heat and humidity, furtherincrease in the efficiency is achieved by reducing the resistance to theflow of the medium in the end parts 12, 13 by means of the shape andparticularly the direction of the protrusions 121, 131 in these parts.

LIST OF REFERENCES

-   1 enthalpy exchanger-   10 lamella (10′, 10 x, 10 y, 10 x ₁, 10 x ₃, 10 y ₂, 10 y ₄)-   100 casing of the exchanger-   11 central part (of the lamella)-   111 protrusion (of the central part of the lamella)-   111′ ridge of the protrusion (of the central part of the lamella)-   111″ ridge of the protrusion (of the central part of the lamella)-   112 longitudinal side of the central part-   113 wall of the casing (of the exchanger upper, lower)-   114 narrow face (of the casing of the exchanger front, rear)-   115 side wall (of the casing of the exchanger)-   12 end part (of the lamella)-   121 (straight) protrusion (in the area of the end part)-   122 (straight) recess (in the area of the end part)-   123 edge (of the end part)-   124 edge (of the end part)-   13 end part (of the lamella)-   131 (straight) protrusion (in the area of the end part)-   132 (straight) recess (in the area of the end part)-   133 edge (of the end part)-   134 edge (of the end part)-   2 channel (flow in direction A)-   3 channel (flow in direction B)-   A direction of flow (from the enclosed space outwards)-   B direction of flow (from the outer space to the inner space)-   DV lower peak (sinusoid)-   HV upper peak (sinusoid)-   R pitch distance of the crests (of the protrusions of the central    part)-   S_(x) sinusoid-   S_(y) sinusoid-   v height of the wave of protrusions (of the central part)-   λ length of the wave of sinusoid S_(x), S_(y)

1. The counter flow enthalpy exchanger (1), having a central part (11)shaped as a rectangular quadrangle, at whose ends it is joined in theflow direction through the exchanger by end parts (12, 13), which becomenarrower in the direction from the central part (11), whereby for theseparation of the flow of the heat transfer medium in the direction fromthe inner space to the outer space are arranged vapour-permeablelamellae (10) with the same area contour which are sealed with respectto the flowing medium and have shaping means for generating turbulentflow, whereby every two adjacent lamellae (10) form in the central part(11) one interplate flow channel characterized in that the lamella (10)is designed as a one-piece self-supporting moulding common to thecentral part (11) and the end parts (12, 13) without a reinforcingsupport grid, whereby every two adjacent lamellae (10) constitute in theend part (12, 13) one interplate flow channel, in whose walls are formedstraight protrusions (121, 131) situated in the direction of the flow ofthe heat-transfer medium between the central part (11) and thecorresponding inlet or outlet of this medium.
 2. The counter flowenthalpy exchanger (1) according to claim 1, characterized in that theself-supporting moulding of the lamella (10) is composite, whereby oneof its components consists of a supporting nonwoven layer, which isconnected to a vapour-permeable membrane.
 3. The counter flow enthalpyexchanger (1) according to claim 2, wherein the material of thevapour-permeable membrane is sulfonated block copolymer.
 4. The counterflow enthalpy exchanger (1) according to claim 2, characterized in thatthe connection of the supporting nonwoven layer with a vapour-permeablemembrane is implemented by moulding or welding or gluing or dipping. 5.The counter flow enthalpy exchanger (1) according to claim 1,characterized in that of the lamellae (10) are interconnected at leastin some parts of the circumference by welding or gluing by means ofairtight joints.
 6. The counter flow enthalpy exchanger (1) according toclaim 1, characterized in that a lamella (10) is made from flat blankswhich are pressed between forming plates having a temperature higherthan 40° C.